Safety of occupants in a vehicle is an important concern to manufacturers and occupants of the vehicles. The manufacturers have disposed seat belts, some partially or wholly inflatable, and inflatable air bags in the vehicles to protect the occupants when collisions involving the vehicle occur. An inflatable member (this term is used herein to include an air bag as) becomes inflated upon the occurrence of a collision involving a vehicle to reduce the occupant's velocity below unacceptable rates and to limit the occupant's movement to enhance the occupant's safety. Many manufacturers have started to provide inflatable members for occupants seated in a front seat.
Perhaps the most significant consideration in a vehicle containing an inflatable member relates to the fact that such a member cannot begin to restrain the occupant's motion during the vehicle collision until the occupant has moved into engagement with such member. Particularly in the case of side protecting air bags, which are typically deployed between the door and the occupant, only a short time is available between the impact and when the occupant begins to move.
The amount of the pyrotechnic material required in the inflators of the prior art have been roughly between fifty percent (50%) to one hundred percent (100%) more than the pyrotechnic material used in the inflator of this invention. As a result, acceptable packaging of the inflatable member and the inflator within a vehicle has been difficult in the prior art.
The configuration and composition of the combustible materials used in existing inflators have also produced relatively slow inflation systems. These slow inflation systems, while sometimes useful for frontal air bags, have not been useful for inflatable seat belts and side impact protection systems since such restraints have to deploy in less than one-fifth of the time for the deployment of a typical air bag. This has been necessitated by the fact that the inflatable belt and the inflatable side bag have to provide occupant protection in much less time than is available for frontal impact air bags. Furthermore, the deceleration distances involved in a side collision and the time interval between the initiation of the side impact against the vehicle and the striking of the occupant against an interior vehicle surface are greatly reduced relative to the distance and time for a front impact.
The combustible materials for some of these systems have also required filters to collect the solid particulates that are produced. The solid particulates required to be filtered in such prior art systems have been excessive. Other systems have been required to utilize relatively large pyrotechnic grains. These grains have been of such size that grain fracture and cracking have occurred and have caused variations in the combustion surface, thereby detrimentally affecting the burning rates within the grains and hence operating pressure and the inflation time.
Furthermore, when large grains have been utilized with slow burning rates, the variations in performance over the range of operating temperatures have been undesirably large. For example, assuming a 40-50 millisecond function time, the changes in the burning rate of the pyrotechnic material have caused the function time of the inflator to vary by approximately .+-.20% when the temperature has been varied between 175.degree. F. and -65.degree. F. This has resulted from changes in the burning rate of the pyrotechnic material with variations in the operating temperature. This considerable percentage change in the burning rate has produced a change in overall function time of approximately 15-20 milliseconds, an appreciable portion of the time available to an air bag to decelerate the movement of the occupant. This change in overall function has produced a resultant variation in occupant protection.
Collisions involving a vehicle at the side of the vehicle are potentially more dangerous than collisions involving a vehicle at the front of the vehicle. one reason is that the vehicle offers very little protection to the occupant when the collision occurs at the side of the vehicle. This results from the fact that only a thin sheet of material defining the side of the vehicle protects the occupant from a collision involving the side of the vehicle.
It has taken years for car manufacturers to accept that inflatable bags should be included in vehicles. The car manufacturers have concentrated on providing inflatable bags to protect the driver and sometimes the other occupant in the front seat from collisions involving the front of the vehicle. The car manufacturers have not concentrated nearly as much in providing an inflatable bag which will satisfactorily protect the driver and the other occupants against side collisions.
In co-pending application Ser. No. 08/587,773 filed on Dec. 22, 1995, for a "System Including an Inflatable Member and an Inflator for Protecting an Occupant in a Vehicle Upon a Collision Involving the Vehicle and Method of Inflating the Member" and assigned of record to the assignee of record of this application, I disclose and claim a system which overcomes the disadvantages and deficiencies discussed above, particularly for front end collisions. The construction and operation of the different sub-assemblies or components in the system of this invention are supplemented by my co-pending application Ser. No. 08/587,773 filed Dec. 22, 1995 which is incorporated in this application by reference.
Prior side air bags proposed have included the air bag arrangements of U.S. Pat. Nos. 5,496,061, 5,464,246, 5,322,322, and 5,282,648.